AU2014240269A1 - A communications cable - Google Patents

Abstract

H:\tld\Intrwovn\NRPortbl\DCC\TLD\68 18808_l.doc-24/09/2014 -14 A communications cable, including a fibre optic cable including a plurality of optic 5 fibres, wherein each one of said fibres is capable of acting as an optic waveguide; an outer jacket layer encasing the optic fibre cable; and a breakout assembly arranged to terminate one end of the fibre optic cable, wherein the assembly provides segregated access to each one of said optic fibres. 1/5 g o IT--

Description

H:\tld\Intrwovn\NRPortbl\DCC\TLD\68 18808_l.doc-24/09/2014 A COMMUNICATIONS CABLE Technical Field of the Invention 5 The present invention relates to a communications cable. For example, the cable is suitable for deployment in outdoor locations. Background of the Invention 10 Telecommunications networks have become critical to modern everyday life. The ability to exchange information over these networks, using devices such as telephones, televisions, computers, smartphones and tablets, significantly influences the social, cultural, and economic development of individuals, organisations and 15 nations. The effectiveness by which information may be exchanged within a communications network is largely dependent on the transmission medium which carries data between endpoints connected to the network. Desirable transmission media have 20 characteristics which enable them to: 1) achieve high throughput in the transmission of data signals, 2) transmit data reliably without loss of information, and 3) be cost effectively manufactured and installed. 25 Optical fibre is a guided medium commonly used in communications networks involving data transmission over large distances. Using a flexible and transparent fibre of extruded glass or plastic, optical fibres transmit information by the propagation of a beam of light between the two ends of the fibre. Optical fibre transmission is enabled 30 by the phenomena of total internal reflection, whereby light incident at a boundary between two optically dense media will be completed reflected if the angle of incidence is larger than the critical angle of the boundary. The critical angle is determined by the difference in the reflective indexes of the media forming the boundary. Optical fibre transmission involves a fibre core, which propagates the light, and cladding layers 35 surrounding the cores providing the reflective boundary necessary for total internal H:\tld\Intrwovn\NRPortbl\DCC\TLD\68 18808_l.doc-24/09/2014 -2 reflection to occur. Optical transmission has significant advantages over other common physical media, such as copper based Unshielded Twisted Pair (UTP) and coaxial cables, including larger bandwidths enabling a higher data transmission rate, and lower susceptibility to signal loss and distortion due to their immunity to 5 electromagnetic interference. Optical fibre cables deployed in practical outdoor environments require robustness to environmental hazards such as exposure to moisture, dirt, temperature, or applied pressure. To achieve this existing outdoor cables are often designed with a "loose 10 tube" structure, whereby buffers are introduced between fibres by applying additional resin type coatings, and by housing the coated fibre in a hollow tube filled with gel or other insulating materials. Furthermore, many outdoor optic fibre cables are required to deliver connectivity to multiple endpoints while enduring exposure to hazardous conditions. Breakout terminations are advantageous in this instance, as the simplex 15 optical fibres are individually jacketed inside an outer housing in order to both facilitate division of the cable connections and to provide the fibres with robustness. In some applications light absorbing glass may also be inserted between the fibres to prevent light leakage introducing losses in adjacent fibres. 20 The above described modifications to improve cable robustness can introduce undesirable effects. For example cable diameter significantly increases (for a fixed bandwidth or number of cores) due to the insertion of the buffered tubes and the use of protective coatings. Cable flexibility is also decreased, with signal losses observed when the fibre is bent around spools or corners. Consequently, existing outdoor optic 25 fibre cables often possess a low fibre-to-conduit ratio, which results in a more expensive manufacturing and installation process since more raw materials are required to produce larger and heavier cables to achieve a given data transfer rate. As global communications networks continue to expand the demand for optical fibre 30 cable transmission media will increase. It is generally desirable to overcome or ameliorate one or more of the above mentioned difficulties, or at least provide a useful alternative. 35 H:\tld\Intrwovn\NRPortbl\DCC\TLD\68 18808_l.doc-24/09/2014 -3 Summary of the Invention According to the present invention there is provided a communications cable, including: 5 (a) a fibre optic cable including a plurality of optic fibres, wherein each one of said fibres is capable of acting as an optic waveguide; (b) an outer jacket layer encasing the optic fibre cable; and (c) a breakout assembly arranged to terminate one end of the fibre optic cable, wherein the assembly provides segregated access to each one of said optic fibres. 10 Preferably, the breakout assembly includes a plurality of furcation tubes extending outwardly from a common end, each one of said furcation tubes acting as a conduit for a respective one of said optic fibres. Preferably, Each one of the furcation tubes has a diameter of 2.0mm. 15 Preferably, the breakout assembly and said end of the fibre optic cable are overmoulded. Preferably, each one of said optic fibres includes an inner core and an outer jacket 20 encasing the inner core. Preferably, the fibre optic cable has a diameter of approximately 5mm. Preferably, the fibre optic cable includes up to 12 individual optic fibres. Brief Description of the Drawings 25 Preferred embodiments of the present invention are hereafter described, by way of non-limiting example only, with reference to the accompanying drawing in which: Figure la is a side perspective view of a communications cable; 30 Figure lb is a side view of the cable shown in Figure la; Figure 2 is a cross section view through the line A-A of the cable shown in Figure 1b; Figure 3a is an end perspective view of the cable shown in Figure la; and Figure 3b is an end perspective view of an alternate communications cable. 35 H:\tld\Intrwovn\NRPortbl\DCC\TLD\68 18808_l.doc-24/09/2014 -4 Detailed Description of Preferred Embodiments of the Invention The communications cable 10 (also referred to as a "small form factor cable") shown in Figures la to 3b includes a fibre optic cable 12 including a plurality of optic fibres 5 14. Each one of the fibres 14 is capable of acting as an optic waveguide. The cable 10 also includes an outer jacket layer 16 encasing the optic fibre cable 12 and a breakout assembly 18 arranged to terminate one end 20 of the fibre optic cable 12. The assembly 18 provides segregated access to each one of the optic fibres 14. 10 As shown, the breakout assembly 18 includes a plurality of furcation tubes 22 extending outwardly from a common end 24. Each one of the furcation tubes 22 acts as a conduit for a respective one of the optic fibres 14. Also as shown, the breakout assembly 18 and the end 20 of the fibre optic cable 12 are overmoulded. 15 As above-mentioned, existing outdoor optic cables achieve robustness by enclosing each individual optical fibre within one or more flexible plastic tubes, which are typically filled with insulating compounds, arranged around a centralised support member. These "loose tube" designs often result in thick, heavy and rigid cables which are costly to manufacture, and which promote low fibre-to-conduit ratios in 20 installations. The communications cable 10 advantageously provides increased optical fibre density and subsequently increased data transmission bandwidth for a fixed cable diameter. The cable 10 is also advantageously robust to environmental hazards. 25 In the described embodiments the communications cable 10 includes a base loose tube optic fibre cable 12. The optic fibre cable 12 includes inner fibre cores 14 available for data transmission, with embodiments including 12 and 6 fibre cores shown in Figures 3a and 3b respectively. However, it will be apparent to those skilled 30 in the art that other embodiments of the communications cable 10 may comprise a base optic fibre cable 12 of different characteristics, including diameter and number of inner fibre cores 14. In such alternative embodiments, the principles for and the methods used in the construction of the described embodiments are also applicable.

H:\tld\Intrwovn\NRPortbl\DCC\TLD\68 18808_l.doc-24/09/2014 -5 As above-mentioned, the communications cable 10 includes a base optic fibre cable 12, an outer jacket layer 16 enclosing the base cable 12, and a breakout assembly 18 that terminates an end section 20 of the optic fibre cable 12. The breakout assembly 18 also provides fibre access via furcation tubes 22. In this embodiment, the base 5 cable 12, outer jacket 16 and first 'input' end 26 of the breakout assembly 18 are cylindrical, with a rectangular assembly output end 28 producing a grid layout of the tubes 22. It will be apparent to those skilled in the art that the base cable 12, jacket 16 and breakout assembly 18 may be constructed with non-cylindrical (such as elliptical or rectangular) cross-sections. In other embodiments, the physical structure 10 of the communications cable 10 may include display elements, which indicate the data transfer state of the cable fibres. The base optic fibre cable 12 and outer jacket structure 16 enclose components which enable electromagnetic signal transmission. As shown in Figure 2, the base optic 15 cable 12 has a diameter of length "X". Preferably, the diameter length "X" is approximately 5.0mm. The base optic cable 12 consists of a collection of inner fibres 14 at the core 202. The individual inner fibres function as a waveguide allowing the transmission of light along the axis of the fibre between the two ends. The fibres as shown consist of dielectrics including an inner core, through which the light signal is 20 propagated, and a cladding layer of refractive index less than the core layer, such that total internal reflection may occur at the core-cladding boundary. In the described embodiment the core layer is 9pm in diameter configured to support a single mode of propagation. The cladding layers are 50pm or 62.5pm in diameter, 25 and may be configured with an abrupt or gradual core-cladding boundary. When operating with abrupt boundary step-indexed fibres, light is injected into the core at an angle greater than the critical angle (as determined by the refractive index differences at the boundary), propagates through the core by reflection, and is received at the other end. When operating with a gradual boundary, the index of 30 refraction in the core is non-constant and decreases between the axis and the cladding. The index profile is chosen to approximate a parabolic relationship between the index and the distance from the axis, with the goal of minimising the axial propagation speeds of the rays in the fibre and reducing multi-path dispersion.

H:\tld\Intrwovn\NRPortbl\DCC\TLD\68 18808_l.doc-24/09/2014 -6 The optic fibres 14 are preferably constructed from silica glass. The refractive index is, for example, 1.62 which may be achieved by doping with materials such as germanium dioxide (GeO2) or aluminium oxide (A1203). Alternatively, the optic fibre cores 14 may be constructed from materials, including but not limited to, 5 fluorozirconate, fluoroaluminate, chalcogenide glasses, and crystalline materials (such as sapphire). The optical fibre cores 14 are surrounded by a cladding layer. In one embodiment the cladding layer used is a dielectric with refractive index of 1.46, although this may be 10 substituted for any number of other dielectric materials with different refractive index values to produce the numerical aperture value required by the embodiment. A buffer coating may be applied to the cladding layer to provide protection against moisture and physical stresses. In the described embodiments cladding buffers are constructed from acrylate polymer or urethane acrylate composite materials, and are applied to 15 the fibre shortly following drawing. Multiple coatings may be applied to the cladding including, for example, an inner coating designed to minimise shock or bending damage, and a second coating to protect against lateral forces. Cladding coatings may be applied, in the described embodiment, by passing the fibre through a primary coating stage, performing UV curing of the resulting first layer, and then repeating this 20 coating and curing process for the secondary layers. Alternatively, the fibre may be subjected to primary and secondary coating phases before experiencing curing. Concentric fibre first and second coatings are applied with typical thicknesses of 125pm and 50pm respectively. The coatings serve to maximise fibre strength and minimise signal attenuation in the presence of stresses. 25 As shown in Figure 2, within the base optic fibre cable 12 the coated optical fibres 14 are packed tightly together in a compact structure, referred to as a loose tube. In some embodiments the coated fibres 14 may be arranged in a helical configuration to reduce fibre stress during stretching of the cable 10 or in response to temperature 30 changes. Flexible fibrous polymer strength members, such as Aramid yarn or Twaron, 204 are wrapped around the inner tube 203 for physical protection. The optical base cable 12 preferably includes additional protective layers 203 and 205 which may be comprised of fluoropolymers, such as polyvinylidene, polytetrafluoroethylene or polyurethene, or a light-weight glass material. The base optical cable 12 has an outer 35 layer 206 comprising of polyvinyl chloride (PVC) or LSZH polymer, or Nylon, which H:\tld\Intrwovn\NRPortbl\DCC\TLD\68 18808_l.doc-24/09/2014 -7 encloses the cable 12 components in a flexible sheath. In other embodiments the tight buffer optic base cable 12 may include additional strengthening members to protect against buckling, and a ripcord for the removal of the outer layer. 5 The outer jacket layer 16 of the cable 10 encloses the base optical fibre cable 12 and provides protection against environmental conditions which may decrease the fibre's performance and/or durability. The cable encapsulated by the outer jacket 16 has a diameter of length "Y". In the described embodiment, the outer jacket 16 comprises a 0.75mm thick coating of polyethylene, where the coating is applied to both the inner 10 and outer surfaces of the base cable 12. The resulting diameter length "Y" is approximately 6.5mm. Application of the outer jacket layer 16 involves extrusion of molten polyethylene over the base cable surface. The polyethylene outer jacket 16 provides the base cable jacket with resistance to 15 hazards including water, moisture, extreme temperatures, UV radiation, organic substances (such as bacteria and fungal growths), and physical stresses, while also producing a cable which is easily ducted. However, it will be apparent to a person skilled in the art that other materials, such as those comprising at least in part of polyvinyl chloride, polyurethane, polyamide, and polybutylene teraphthalate, may be 20 used to construct the outer jacket layer 16. In some embodiments the outer layer may be colour coded to indicate the type of fibre and/or the transmission capability of the enclosed optical cable. The scheme used in the described embodiment is the Tia/EIA 598 standard for optical fibre colour coding, or any other colour. 25 The breakout assembly 18 is coupled to the end 20 of optic fibre cable 12 by an overmoulding. The breakout assembly 18 in the described embodiment possesses, at least, an outer surface constructed from a similar material as that used in the construction of the optical cable outer jacket. The breakout assembly 18 provides access to each individually coated optical fibres 14 within the base optical fibre cable 30 12 via the furcation tubes 22. The embodiment shown in Figure 3a includes an assembly 18 with 12 furcation tubes 22 which corresponds to the number of individual fibres 14 within the base optical cable 12. The embodiment shown in Figure 3b includes an assembly 18 with 6 furcation tubes 22 which corresponds to the number of individual fibres 14 within the base optical cable 12. 35 H:\tld\Intrwovn\NRPortbl\DCC\TLD\68 18808_l.doc-24/09/2014 The furcation tubes 22 are preferably 2.0mm in diameter and may comprise of an inner tube for housing the 250pm buffered optical fibre 14, an inner protective layer of Aramid yarn, and an outer protective layer constructed from polyvinyl chloride (PVC), LSZH, or another material providing similar durability, robustness and flexibility 5 properties. In another embodiments the furcation tubes may each contain a pull string constructed from materials such as Aramid yarn. Each individual optical fibre furcation tube 22 may be used as a patch cable to provide data connectivity to the intended termination application. Connection of each furcation 10 tube 22 at the application destination may be achieved by the use of a common connector type, such as Avio, ADT-UNI, DMI, EC, ESCON, FC, SC, SCA, ST, LC, MTRJ, SMA, and other variants known to persons skilled in the art. In other embodiments the furcation tubes 22 may be connected to a terminal using fibre optic path panels, or an optical distribution frame. The optical fibres 14 housed by the furcation tubes 22 may 15 alternatively be extended by connection to other optical fibres by splicing. The outer jacket 16, the enclosed base optical fibre cable 12, and the breakout assembly 18 are coupled together via an overmoulded sheath. In the described embodiment, the overmould material is melted and forced into a mould cavity by high 20 pressure injection. A thermoplastic moulding process may be followed involving feeding the raw jacket materials into a heated barrel with a screw used to deliver the material while simultaneously reducing heating time required through the application of shearing forces. The polyethylene based material may then be fed through a check valve until sufficient pressure builds to force the material into the one or more mould 25 cavities. In the described embodiment the mould cavity comprises the outer cable jacket structure 16 and at least part of the breakout assembly 18 such that both components are physically and inseparably attached. Injection for the construction of a single 30 mould ceases when the mould cavity is filled, and the mould may then be cooled using methods including free standing or cooling lines. It will be apparent to the skilled person in the art that the overmoulding process used may vary based on the exact material composition of the outer jacket and breakout assembly fixture components.

H:\tld\Intrwovn\NRPortbl\DCC\TLD\68 18808_l.doc-24/09/2014 -9 The communications cable 10 may be implemented as a data transfer medium for telecommunications and networking applications. For the configuration described, modulation rates of between 10 and 40 Gbit/s are typical for light signals within each channel. Wavelength division multiplexing (WDM) may be employed to allow each 5 fibre to carry multiple independent channels. The cable 10 may also be applied to fibre optic sensor applications, whereby the optical fibres 14 may be either configured as sensors, or used to connect external sensors to the measurement system. The additional robustness provided to pressure, 10 moisture, temperature and tensile stresses, in combination with the reduced diameter cable may allow the deployment of remote sensing in hazardous environments. For example, extrinsic fibre optic sensors may be used to measure temperature inside aircraft engines via the transmission of radiation, and to measure the internal temperature of electrical transformers. The described communications cable 10 may 15 also be advantageous when deployed for the purpose of sensing in intrusion detection systems due to their reduced size. Other applications of the communications cable 10 include power transmission, where photovoltaic cells may be utilised to convert the light carried by the fibres into 20 electricity. The described communications cable 10 provides a more compact transmission medium for the light transfer, which is advantageous when power must be supplied to electronics in antennas or other isolated equipment. Many modifications will be apparent to those skilled in the art without departing from 25 the scope of the present invention The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that the prior art forms part of the common general knowledge in Australia 30 In this specification and the claims that follow, unless stated otherwise, the word "comprise" and its variations, such as "comprises" and "comprising", imply the inclusion of a stated integer, step, or group of integers or steps, but not the exclusion of any other integer or step or group of integers or steps. 35 H:\tld\Intrwovn\NRPortbl\DCC\TLD\68 18808_l.doc-24/09/2014 - 10 References in this specification to any prior publication, information derived from any said prior publication, or any known matter are not and should not be taken as an acknowledgement, admission or suggestion that said prior publication, or any information derived from this prior publication or known matter forms part of the 5 common general knowledge in the field of endeavour to which the specification relates.

H:\tld\Intrwovn\NRPortbl\DCC\TLD\68 18808_l.doc-24/09/2014 - 11 List of Parts 10 Communications cable 12 Optic fibre cable 5 14 Optic Fibre 16 Outer jacket layer 18 Breakout assembly 20 End of fibre optic cable 22 Furcation tube 10 24 Common end of breakout assembly 26 First input end of breakout assembly 28 Output end of breakout assembly 202 Air 203 Protective layer 15 204 Flexible fibrous polymer strength members 205 Protective layer 206 Outer layer 207 Protective layer, Sacrificial Sheath 20 25

Claims (9)

1. A communications cable, including: (a) a fibre optic cable including a plurality of optic fibres, wherein each one 5 of said fibres is capable of acting as an optic waveguide; (b) an outer jacket layer encasing the optic fibre cable; and (c) a breakout assembly arranged to terminate one end of the fibre optic cable, wherein the assembly provides segregated access to each one of said optic 10 fibres.

2. The communications cable of claim 1, wherein the breakout assembly includes a plurality of furcation tubes extending outwardly from a common end, each one of said furcation tubes acting as a conduit for a respective one of said optic fibres. 15

3. The communications cable of claim 2, wherein each one of the furcation tubes has a diameter of 2.0mm.

4. The communications cable of any one of claims 1 to 3, wherein the breakout 20 assembly and said end of the fibre optic cable are overmoulded.

5. The communications cable of any one of claims 1 to 4, wherein each one of said optic fibres includes an inner core and an outer jacket encasing the inner core. 25

6. The communications cable of any one of claims 1 to 5, wherein said fibre optic cable has a diameter of 5mm.

7. The communications cable of any one of claims 1 to 6, wherein the fibre optic cable include up to 12 individual optic fibres. 30

8. The communications cable of any of claims 1 to 7, wherein said outer jacket layer includes one or more of polyethylene, polyvinyl chloride, polyurethane, polyamide, and polybutylene teraphthalate. 35

9. The communications cable of any one of claims 1 to 8, wherein the outer jacket H:\tld\Interwoven\NRPortbl\DCC\TLD\68 18808_l.doc-24/09/2014 - 13 layer encasing the optic fibre cable is 6.5mm in diameter.